1. Field of The Invention
This invention relates to esters of .beta.-acryloxy-propionic acid and other Michael addition homopolymers of acrylic acid, polymers of the esters and applications for the monomers and polymers, such as in formulations for coatings, binders and adhesives. The esters of vinyl addition monomers, many of which are particularly adapted for use as reactive diluents, modifiers and crosslinkers in compositions comprising polymeric materials, are especially useful in systems cured by radiation or autoxidation.
2. Description Of The Prior Art
Preparation of the homopolymer of acrylic acid has been described in Polymer Letters Edition, Volume 14, pages 277-281, 1976; Macromolecules, Volume 7, pages 256-258, 1974; U.S. Pat. No. 3,888,912; and European Patent 3045. The European Patent and U.S. Pat. No. 4,048,259 disclose the use of the homopolymer acid in adhesives and U.S. Pat. Nos. 3,266,930 and 4,048,259 disclose its use in coatings as well. U.S. Pat. No. 3,868,410 teaches the recovery of acrylic acid, an alkanol and an alkyl acrylate from an alkyl ester of the acrylic acid Michael addition homopolymer.
Government implementation of ever more stringent antipollution regulations has generated considerable interest in the development of reactive diluents in coating compositions. Ideally, these diluents are high boiling (i.e. essentially nonvolatile), low viscosity monomers that function as solvents for polymeric constituents during application but can subsequently be induced to polymerize, i.e. can undergo a curing process of some kind, thus becoming an integral part of the final product. Pollution attributable to conventional solvent emissions is thereby reduced or eliminated. There is also a great need, in such coating systems, for multifunctional monomers, with similar physical characteristics, that can serve as crosslinkers capable of providing desirable coating properties, especially mechanical and resistance properties. Unfortunately, many of the reactive diluents and crosslinkers currently in use suffer one or more of the following significant disadvantages: (1) excessive volatility under the conditions of use, (2) less than optimum handling characteristics (i.e., poor solubility in or compatibility with common polymeric materials, crystallinity, high viscosity, etc.) or (3) unacceptable toxicological effects.
The esters of the instant invention are particularly useful as reactive diluents, modifiers and crosslinkers when admixed with other polymeric materials. They are lower in volatility and surprisingly lower in toxicity than acrylate analogues while still retaining desirable viscosity and reactivity properties as compared to the analogues. The esters of the homopolymers of acrylic acid (AOnPA), also referred to as AOnPAtes hereinbelow, are more hydrophobic than the corresponding acrylates and thus more compatible with many conventional polymers and formulations in, for example, coatings, binders and adhesives.